Germanium-silicon light sensing apparatus
A method for fabricating an image sensor array having a first group of photodiodes for detecting light at visible wavelengths a second group of photodiodes for detecting light at infrared or near-infrared wavelengths, the method including forming a germanium-silicon layer for the second group of photodiodes on a first semiconductor donor wafer; defining a first interconnect layer on the germanium-silicon layer; defining integrated circuitry for controlling pixels of the image sensor array on a semiconductor carrier wafer; defining a second interconnect layer on the semiconductor carrier wafer; bonding the first interconnect layer with the second interconnect layer; defining the pixels of an image sensor array on a second semiconductor donor wafer; defining a third interconnect layer on the image sensor array; and bonding the third interconnect layer with the germanium-silicon layer.
1. A method for fabricating an image sensor array having a first group of photodiodes for detecting light at visible wavelengths, and a second group of photodiodes for detecting light at infrared or near-infrared wavelengths, the method comprising:
forming a germanium-silicon layer for the second group of photodiodes on a first semiconductor donor wafer;
defining a first interconnect layer on the germanium-silicon layer, wherein the first interconnect layer includes a plurality of interconnects configured to be coupled to the first group of photodiodes and the second group of photodiodes;
defining integrated circuitry for controlling pixels of the image sensor array on a semiconductor carrier wafer;
after defining the integrated circuitry, defining a second interconnect layer on the semiconductor carrier wafer, wherein the second interconnect layer includes a plurality of interconnects coupled to the integrated circuitry;
bonding the first interconnect layer with the second interconnect layer;
defining the pixels of an image sensor array on a second semiconductor donor wafer;
after defining the pixels of the image sensor array, defining a third interconnect layer on the image sensor array; and
bonding the third interconnect layer with the germanium-silicon layer, such that the first group of photodiodes and the second group of photodiodes are coupled to the integrated circuitry.
2. The method of claim 1 , further comprising:
after bonding the first interconnect layer with the second interconnect layer, removing the first semiconductor donor wafer.
3. The method of claim 1 ,
wherein forming the germanium-silicon layer for the second group of photodiodes on the first semiconductor donor wafer comprises growing a blanket layer of germanium-silicon on the first semiconductor donor wafer, and
wherein the method further comprises:
after bonding the first interconnect layer with the second interconnect layer, defining regions for at least the second group of photodiodes on the germanium-silicon layer.
4. The method of claim 1 ,
wherein forming the germanium-silicon layer for the second group of photodiodes on the first semiconductor donor wafer comprises:
depositing an insulating layer on the semiconductor donor wafer;
defining, on the insulating layer, regions for the second group of photodiodes; and
growing a germanium-silicon layer on the regions for the second group of photodiodes.